Adrian Goodman's Research Interests
THE MECHANICS OF RETTING IN HEMP
sativa) is widely grown for its fibres; it produces phloem fibres,
which are formed in
bundles towards the periphery of the stem. In order to remove the fibre from
the stem it is left to decompose by the action of fungi and bacteria, this
process is called retting. This
study investigated one aspect of the retting process, the dissociation
of these fibres from the core of the stem.
Peel tests were used to investigate the work required to remove a tissue peel, rich in fibres, from the core of the stem. Two separate experiments studied (1) the effects of tissue dehydration as stems were dried out in the oven; and (2) the progress of retting in stems that were dew-retted in the field.
As the plant tissues dehydrated their fracture characteristics changed and this was reflected in the increase in the work to peel seen in the oven-dried samples. This, however, was not evident in the field-retted samples, in which there was a decrease in work to peel (Fig. 1). The field-retted samples were exposed to the activity of micro-organisms for a prolonged period of time compared with the oven dried samples; this increased the potential degradation caused by microbial enzymes. Thus, the reduced work to peel in dew-retted stems is thought to be due to the colonisation of the stem by micro-organisms and the subsequent retting process. The dramatic decrease in work to peel at low moisture content in the oven-dried stems is thought to result from mechanical changes leading to brittle fracture characteristics.
A comparison of the work to peel in oven-dried and dew-retted stems.
Solid squares represent
while open squares represent dew-retted stems.
study indicates that peel tests can be used to objectively monitor the
reduction in work to peel for dew-retted stems and relate this reduction
to the progress of retting. Thus, peel tests may be used to monitor the
effects of different factors on the process of retting in hemp.